textproduct: Rapid City

KEY MESSAGES

- At or below normal temperatures for the remainder of the weekend.

- Rainfall chances overnight looking a little less likely, with better chances coming Sunday night

- Seasonal temperatures through the week, with rainfall chances returning by midweek.

UPDATE

Issued at 918 PM MDT Sat Sep 12 2026

Evening updates were mainly focused on the winds and chances of precip. For tonight, kept the rain chances to south central SD and mainly after 10PM with low end rain chances lasting through the overnight hours. Another round of precip from the southwest is looking likely late Sunday into early Monday. A projected surface low looks to develop near north central WY Sunday afternoon before tracking northeast Sunday night. This would give NE WY and W SD a decent chance at passing rain and thundershowers.

With respect to the winds, allowed wind gusts to be decreased from inherited forecast. The forecasted wind gusts for Sunday were decreased after reviewing latest hi-res guidance, ensembles, and wind gust probabilities. That being said, wind gusts around 35 to 45 mph are likely in the NW WY and SD plains with isolated gusts to near 50 possible. So it will still be a windy day but, at least for now, headlines don't look to be needed. Monday is a different story with forecasted wind gusts upwards of 40 to 50 mph for NW SD are looking a little more likely. Stay tuned.

DISCUSSION

(This Evening Through Saturday) Issued at 1237 PM MDT Sat Sep 12 2026

Latest water vapor imagery shows broad upper high pressure located across the southern tier of the country with a digging 500hpa low off of the Pacific NW coast. Quick moving zonal flow is found across the upper midwest. At the surface high pressure is located across much of the western Dakotas with a weak surface trough sliding southeast across eastern SD. At 18Z skies were mainly clear to partly cloudy except for along the ND/SD border where more clouds were found. Temperatures were in the mid 50s to mid 60s.

Models are still advertising 700hpa theta-e ridge and associated forcing to slide across southern tier counties overnight. Did trim back inherited pops but am still a bit concerned that we might be overdoing the forecast. Ensembles are only showing 10-20 percent probabilities of seeing greater than 0.01 inch of rain across our southern counties, and less than that of seeing 0.05 inch of rainfall.

Sunday will looks to be dry to begin with and becoming breezy with easterly upslope flow. This will result in a few more clouds which will aid in keeping temperatures down a bit more. Sunday night into Monday morning main upper trough finally kicks out across region with associated 700hpa theta-e ridge and forcing. Better moisture tracks along with this feature and this is when our best chance of seeing rainfall occurs. As the moisture shield tracks west to east it will become more widespread. Expecting more to fall is rain, although can't rule out some scattered thundershowers here or there through the period.

The remainder of the week looks to be seasonable temperature wise, with rainfall chances returning back to the forecast area around mid-week.

AVIATION

(For the 12Z TAFS Through 12Z Monday Morning) Issued At 535 AM MDT Sun Sep 13 2026

VFR conditions are expected through the TAF period. Breezy southeast winds will develop over the area by this afternoon with gusts of 25-35kt over the plains. TSRA may move into the area this evening, expect LCL MVFR conditions near any cells.

UNR WATCHES/WARNINGS/ADVISORIES

SD...None. WY...None.